WILLIAM BATESON——-MORGAN 525 
than Darwin’s view, if only because the mutation theory demands a 
more objective and rigorous answer than one that might have suf- 
ficed in Darwin’s time. The points raised by Bateson are the fol- 
lowing: If mutants are incipient species, why has no infertility 
been observed between any mutant and its parent type, the in- 
dividuals of the new type being fertile inter se? If infertility 
does not arise in the single step, what reason can be given for sup- 
posing that more steps will lead to infertility? That this point is 
well taken, no one familiar with the mutation process is likely to 
deny. The tables might, perhaps, be turned by stating that when 
such a mutation does occur it will give rise to a new species in the 
sense defined. But such a counter-argument would be foolhardy, 
both because it concedes too much to the restricted definition of 
species and also because it appeals to something not yet observed. 
It is true that Plough has recently observed a case in which a mutant 
type appeared that is more fertile with others of its kind than with 
the parent type, but a single case of this sort, not yet fully reported, 
is a dangerous precedent to appeal to. The point that Bateson has 
made was, I believe, well made. He scorned to take an easy road 
to success if in taking it, a difficulty is ignored, and we will do well, 
I think, to follow his example, which, after all, involves only waiting 
to see whether a solution may not be found. One possible source 
of hopefulness may at least be pointed out. Practically all the cases 
of mutant changes that have been observed and studied relate to 
external characters that can not be supposed to have anything to 
do with physiological functions causing infertility. It is the latter 
that must be involved when species are infertile inter se. There is 
no good reason to expect that any of the recorded mutant types should 
have been infertile with the parent type. Moreover, if a mutant 
individual should appear that was infertile with the parent type 
it is unlikely that it would be, or even could be, tested at the time 
with one of its kind, ete. Bateson intended no doubt that the point 
he raised should not be simply one of carping criticism—he was 
singularly free from raising a question in that spirit—but rather 
that it might lead to observations in a direction that would bear 
directly on the point at issue rather than to take something for 
granted that had not been proven. 
“The second difficulty that Bateson has raised is perhaps not so 
serious. The sterility of the hybrid (which is generally regarded 
as a more decisive feature of specific distinction) has not been ob- 
served for any new types that have a known mutational origin when 
mated to the parent type. It is generally known that the sterility 
of the hybrid is a very variable condition. It has been shown in a 
number of cases to result from failure of the conjugation of the 
chromosomes at maturation, which leads, automatically, to great 
